Fractional distillation of crude oil Flashcards
What is crude oil?
Crude oil is a mixture of mostly alkanes, both branched and unbranched
What does crude oil contain besides hydrocarbons?
Crude oil contains small amounts of other compounds, like sulfur containing compounds
How do sulfur compounds in crude oil contribute to pollution?
When burnt, sulfur compounds produce sulfur dioxide
How is sulfur trioxide formed in the atmosphere?
Sulfur dioxide reacts with oxygen high in the atmosphere to form sulfur trioxide
What happens when sulfur trioxide reacts with water in the atmosphere?
Sulfur trioxide reacts with water to form sulfuric acid
What environmental issue is cause by the formation of sulfuric acid from sulfur compounds in crude oil?
The formation of sulfuric acids contributes to acid rain
What is the process called that separates crude oil into useful products?
Fractional distillation
How are the fractions in fractional distillation separated?
By heating the crude oil and collecting the fractions that boil, over different temperature ranges
What does each fraction consist of?
A mixture of hydrocarbons with similar chain lengths and properties
Describe the rel of bubble caps in the fractionating tower?
Vapours pass through bubble caps on trays until they reach a tray cooler than their boiling point, where they condense into liquids
Where do short chain hydrocarbons condense in the fractionating tower?
Near the top of the tower, where it is cooler, because they have lower boiling points
What is the thick residue that collects at the base of the tower called?
Tar or bitumen
What is tar/bitumen used for? What happens when supply exceeds demand?
It is used for road surfacing, but when supply exceeds demand, it is further processed to produce more valuable products
What is the full process of fractional distillation using the fractionating tower?
7 stages
- Crude oil is heated in furnace
- Mixture of liquid and vapour passes into tower, being cooler at the top than bottom
- Vapour passses up the tower through a series of trays containing bubble caps until they arrive at a tray that is sufficiently cool
- It then condenses into a liquid
- Mixture of liquids that has condensed is piped off each tray
- Shorter chain hydrocarbons condense in trays nearer to top of the tower, where it is cooler
- A thick residue is left at the base of the tower call tar, used for road surfacing
Why do shorter chain hydrocarbons condense in trays nearer to the top of the tower?
This is because they have lower boiling points
What type of process is fractional distillation?
It is a physical process
Are covalent bonds broken during fractional distillation?
What type of forces are broken during vaporisation in fractional distillation?
Covalent bonds within the molecules are not broken during fractional distillation. Van der Waals forces between the molecules are broken during vaporisation
What happens to the van der Waals forces during condensation in fractional distillation?
Van der Waals forces reform between the molecules during condensation